Packing cartons of products into boxes is just one of many tasks that are required to provide an efficient and speedy production line. Where the cartons are of simple shape it is not a significant problem. However some product cartons do not lend themselves readily to be automatically handled and packed into boxes. Milk and juice cartons are one example of this type of product carton. Such products are often packaged in cartons that are made of coated paper or board stock, formed into a rectangular shaped tube. The tube is formed with a sealed flat base and is squeezed together at its upper end and is sealed at the top by a heat sealed seam. For efficient handling cartons must be packed into boxes for shipment. These cartons come in a variety of sizes. They may be single serving size, or may hold a pint or a quart of liquid, and in some cases more.
Handling such cartons in an automatic packing line requires that they can be grasped, without squeezing the sides, lifted, in a group, such that the group will fit into one layer of the box, moved over into registration with an open box, lowered into the box, and the group of cartons must then be released in the box. This action must be repeated as often as required to fill the box. When filled the box will be transferred to a box sealer, and a fresh unfilled box moved into its place.
All of these steps must be carried out in a continual sequence so that the packing operation may be incorporated in a continuous moving conveyor line. Grasping of the cartons presents its own problems. Due to the liquid contents of the cartons, they represent relatively substantial weight per unit of carton size. Also due to the liquid content the cartons cannot be grasped by their sides. The sides of the cartons are somewhat thin and flexible, and can be inwardly deflected by even modest pressure. Consequently it is desirable to grasp the cartons and lift them by holding the heat sealed seam along the top. This can withstand substantial pressure. However it is has a relatively low height In addition it is located along a line bisecting the rectangular section of the carton. Thus where cartons of a first size may define a first distance on each side of the seam, cartons of second size, either larger or smaller, will define a second distance on either side of the seam. This difference in size will require adjustment of the spacing between the gripping devices which grip to top seams of the group of boxes.
The packing machine must thus be such that it can, with certain modifications, grasp, lift, transfer and release, groups of cartons which are in a range of different sizes, depending on the size on cartons being filled and packed at a particular time.
Preferably there are two transfer portions of the packing machine. They will move along an axis transverse to the flow path of the conveyor system. It is advantageous if there are two side by side conveyor paths, with the unfilled box being located between them. In this way the packing machine can move a first packing portion from from the one conveyor to the unfilled box. At the same time a second packing portion of the machine is moving from the box location back to the other conveyor. At this point the second packing portion will grasp a group of cartons from the second conveyor line and move over the box, release them and return to the second conveyor line and so on. In this way the cartons on one conveyor can be allowed to accumulate into a group, ready for transfer, while a group of cartons from the other conveyor is being grasped and transferred to the box.